This invention relates to machine tool numerical control systems in general and more particularly to improved machine tool control system of the type operated from perforated tape which permits changing and adding data.
Machine tool controls of the general type with which the present application deals are well known in the art and are disclosed, for example, in Siemens-Zeitschrift Vol. 47 (1973), Supplement entitled "Controls and Drives for Automatic Machine Tools", pages 8 to 11.
In the art of numerical control of machine tools a program is prepared by a programmer in accordance with the requirements of the work piece and the machine. This program is transferred to perforated tape or the like and using the perforated tape, a test run is made on the machine tool. Frequently it turns out that the program still contains errors, possibly because of the incorrect programming of coordinate values or because feed speeds or spindle speeds where chosen to be too high or two low. Presently, it is customary to note the necessary corrections and return them along with the perforated tape to a programming department which has available the necessary equipment for making a new tape. The new tape is then prepared taking into consideration corrections. This necessity to return the tape for correction leads to an undesireable lengthening of the overall processing time and furthermore results in idle machine time. Alternatively, it necessitates resetting the machine to a new work piece in the meantime. In view of these problems direct correction of the tape at the machine is extremely desirable.
One possible solution to this problem would be to write the entire program into an electronic memory associated with the numerical control and to correct programs stored therein by deleting incorrect and adding missing information. However, to do so requires storage means of a size tailored to the largest possible overall program to be stored on perforated tape. As a result, a potentially very large memory is required. This adds to the overall expense and, furthermore, with this type of correction scheme, there is the danger of unintentional intervention in correct portions of the program.
A further problem arises in connection with supplementing and expanding information for the control of the machine tool if the geometrical information and technological information are separated in the preparation of the program. What is meant by geometrical information is information relating to the desired shape of work piece and is independent of the material and machine used. Technological information relates to the specific machine and material being worked, i.e. speeds, etc.
It is of great advantage that geometric information, which supplies the bulk of the data be available to always be taken from the same perforated tape and this information supplemented only in dependence on the machine used.
In view of these various deficiencies in the prior art and the desireability of having the noted capabilities, the need for a new machine control system utilizing numerical control becomes evident.